Method of simultaneously defatting,dehydrating,and eliminating bacteria from foodstuffs

ABSTRACT

STERILIZATION IS ACCOMPLISHED BY CONTACTING MICROORGANISMS WITH METHOXYMETHANE. FOODSTUFFS ARE ALSO DEFATTED AND/OR DEHYDRATED BY SOLVENT EXTRACTION WITH METHOXYMETHANE, OR DIMETHYL ETHER, AS IT IS ALSO CALLED.

United States Patent O 3,795,750 METHOD OF SIMULTANEOUSLY DEFATTING,

DEHYDRATING, AND ELIMINATING BAC- TERIA FROM FOODSTUFFS Irving E.Levine, Mill Valley, Calif., assignor to Chevron Research Company, SanFrancisco, Calif.

No Drawing. Continuation-impart of application Ser. No.

337,238, Mar. 1, 1973, which is a continuation of applications Ser. No.65,695, Aug. 20, 1970, and Ser. No. 238,601, Mar. 27, 1972, said Ser.No. 238,601 being a continuation-in-part of application Ser. No.163,532, July 8, 1971, which in turn is a continuation-impart ofapplication Ser. No. 65,695, Aug. 20, 1970, all now abandoned. Thisapplication Mar. 2, 1973, Ser. No. 337 519 Int. Cl. A22c 18/00; A23]:1/00, 1/04 US. Cl. 426-332 2 ABSTRACT OF THE DISCLOSURE Sterilization isaccomplished by contacting microorganisms with methoxymethane.Foodstuffs are also defatted and/or dehydrated by solvent extractionWith methoxymethane, or dimethyl ether, as it is also called.

CROSS-REFERENCE TO RELATED APPLICATIONS This application is acontinuation-in-part of copending application Ser. No. 337,238, filedMar. 1, 1973, which, in turn, is a continuation of applications Ser. No.65,695, filed Aug. 20, 1970, and copending application Ser. No. 238,601,filed Mar. 27, 1972. The aforesaid application Ser. No. 238,601 is acontinuation-in-part of copending application Ser. No. 163,532, filedJuly 8, 1971, which, in turn, is a continuation-in-part of applicationSer. No. 65,695, filed Aug. 20, 1970. All of the aforementionedapplications are now abandoned in view of the present application.

BACKGROUND OF THE INVENTION This invention relates to sterilization withmethoxymethane. More particularly, the invention concerns thesterilization of areas or articles contaminated by microorganisms,including foods and beverages, by contacting them with methoxymethane.

Sterilization of areas or materials ordinarily involves the applicationof stringent measures such as heating, adding chemical preservatives,chemical treating, or radiation. These stringent measures havesubstantial drawbacks, especially so far as foods and beverages areconcerned. Sterilizing with heat requires elevated temperatures whichare impractical for general application involving wide areas or largematerials, and the heating also may cause undesirable alterations in theflavor and texture of the material sterilized, as in the case of foodsand beverages. Chemical additives leave a residue and may change theappearance and taste of the sterilized material, as chemical treatmentmay also, as in the case of sulfur dioxide treatment of food such asraisins and dried prunes and beverages such as wines. Radiation causesflavor and texture alterations as well as involving various operatingdifficulties that make it hazardous to use.

This invention also relates to the extraction of normally solidfoodstuffs, such as meat and vegetables, as distinct from liquid, suchas milk and fruit juices, with methoxymethane, also called dimethylether, to remove water and fat as well as other materials soluble in thedimethyl ether, for example, cholesterol.

As obtained from natural sources, such as from animals, vegetables,fungi, bacteria, or algae, food is mainly composed of four classes ofsubstances. These are pro- 3,795,750 Patented Mar. 5, 1974 tein, fat,carbohydrates, and water. In its natural form, food has a tendency tospoil; some of its ingredients are considered undesirable from a healthstandpoint; and its often substantial water content not only facilitatesspoilage but also contributes undesirable bulk and weight, which makesits transportation more difficult and costly. These problems have beenrecognized for many years. Foods have been preserved by drying even byprimitive peoples. Sterilization and canning are now common practice.More recently, freeze drying has proved to be effective but costly.Within the last century, nonfat dried milk has become a major article ofcommerce worldwide.

SUMMARY OF THE INVENTION An improved sterilization method has now beenfound which comprises contacting microorganisms in an area or articlewith methoxymethane. After sterilization the area or article sterilizedis preferably protected against introduction of microorganisms as, forexample, by the use of a protective wrapper, container, or the like.

In particular, substances of the class consisting of foods and beveragesare effectively sterilized or preserved by contacting the substanceswith methoxymethane and protecting the sterility of the substance.Similarly, areas or articles in general are sterilized and protected.

The sterilization or preserving methods of the present invention havemany advantages compared to previous techniques. Because of the lowboiling point of methoxymethane heat is not required and there are noneof the usual undesirable side effects due to the use of elevatedtemperatures. Also, the relative chemical inertness of themethoxymethane insures against the presence of residues which may changethe flavor, texture and/or appearance as would be particularlyobjectionable in the case of foods and beverages.

An improved method of-defatting and/or dehydrating normally solidfoodstuffs of animal, vegetable or microbial origin, has also now beenfound which comprises subjecting said foodstuffs to a solvent extractionwith liquid dimethyl ether, usually at temperatures below 30 C., andseparating the dimethyl ether extractant solution.

The dimethyl ether has unique properties for extracting both water andfats, as well as certain other substances soluble in the dimethyl ether,which make it possible to prepare normally solid foodstuffs, such asmeat and vegetables, in a substantially dried and low fat form, in whichform the food can be stored for long periods of time without takingspecial precautions such as sterilization, refrigeration or freezing, orfreeze drying. The unique properties of dimethyl ether which make itpossible to accomplish these valuable results in a more economicalmanner than by other known processes are its low boiling point and easeof removal from the extracted food product, thereby eliminating thepossibility of trace residues of the extractant; dimethyl ethers lowlevel of taste and odor; its lack of toxicity; its ability to dissolveboth water and fatty materials; and, finally, its relative chemicalinertness. Dimethyl ether does not form peroxides upon exposure to airin the way that diethyl ether does, for example; nor does it formcondensation products in the way acetone does. This lack of chemicalreactivity under conditions of use avoids the formation of undesirableflavors and odors.

An added advantage of the present method is the concurrent extraction ofwater along with the fat. The ability of the process to remove bothwater and fat is particularly important because in the case of somefoodstuffs it seems that water may act to prevent completely effectiveextraction of the fat, as in the case of extraction with diethyl ether.

The defatted and/or dehydrated foodstuff prepared in accordance with themethod of the present invention is conveniently reconstituted to edibleform. For example, water may be added as required, and the foodstuffheated or cooked, as by frying, in any of the commonly used edible fatsor oils. Optionally, a fat either the same or different from thatremoved in the extraction may also be added at any desired concentrationto give a more completely reconstituted food.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Methoxymethane or dimethylether, as it may also be termed, has the formula C H O. It is acolorless gas and has a slight ethereal odor. It is normally kept as aliquefied gas under its own vapor pressure of 60 pounds per square inchgauge at 70 F. Although methoxymethane is an ether, it is unusual inthat it does not form peroxides under normal storage and use conditions.

The methoxymethane can be used as a sterilant in several forms,including pure liquid methoxymethane, solutions in other liquids, suchas water, and gaseous methoxymethane. Preferably, gaseous methoxymethaneis used in the presence of water vapor for maximum effectiveness.

Any suitable means of contacting microorganisms in an area withmethoxymethane may be used. In the treatment of articles or confinedareas of microorganisms such as encountered in the processing of foodsand beverages, the microorganisms are suitably contacted withmethoxymethane under pressure, usually in liquid form. Methoxymethanesolutions are thereby formed with liquids normally present in the foodsand beverages. In many instances the article sterilized may be contactedwith liquid methoxymethane, which is then allowed to evaporate, thusproviding both liquid and gas contacting of the microorganisms. In thetreatment of large areas such as pressure chambers and the like,methoxymethane gas under pressure is conveniently employed.

In the sterilization of foods and beverages the typical microorganismsare most effectively controlled by contacting with methoxymethane atpressures sufficient to maintain liquid state, usually in the range offrom about 30 to about 75 pounds per square inch or higher. Contacttimes adequate to kill the microorganisms are used, ordinarily rangingfrom as brief as one minute to as long as one hour or more. Although aparticular advantage of sterilization with methoxymethane lies in itseffectiveness at ambient or room temperatures, either lower or highertemperatures may be employed as desired as, for example, to maintainliquid contact or to evaporate dissolved methoxymethane.

Any concentration of the methoxymethane may be used so long as it is aneffective amount sufficient to reduce the microorganisms in thecontacted area. The concentration of methoxymethane may be varieddepending on the pressure, time, and temperature conditions. In the caseof the sterilization of liquids sufficient methoxymethane to provide apartial pressure of about pounds per square inch is desirable foreffective sterilization.

The microorganism contacted by the methoxymethane in accordance with theprocedure of the present invention may be any bacteria or protozoa. Inthe case of foods and beverages certain particular organisms areeffectively controlled. Examples include in milk processingLactobacillus bulgaricus, Streptococcus cremoris, Escherichia coli,Clostridium perfringens, and Staphylococcus aureus; in food processingStaphylococcus aureus and Salmonella typhimurium.

Following the sterilization, removal of methoxymethane as desired isreadily achieved by venting the sterilized area to the atmosphere.Because of the low boiling point of methoxymethane very little residueremains after evaporation under tl lllfil QOHditiOHS- In the case ofsterilization of liquids such as beverages where the methoxymethane maybe in solution, stripping is effectively accomplished, either byapplying a vacuum, sparging with an inert gas, or by raising thetemperature if necessary. If many of the sterilization proceduresadaptable to closed systems and methoxymethane is recovered followingits separation and is available for recycling or further use.

After the microorganisms of an area are contacted and sterilized oreffectively controlled, it is desirable in most cases to protect thesterilized area against introduction of other microorganisms. In thecase of foods and beverages containers such as cans and bottlescustomarily provide such protection. Other enclosure means such aswrapping with films and the like may also be useful.

The dimethyl ether extraction of foodstuffs in accordance with themethod of the present invention is relatively straightforward andinvolves little in the way of complex procedures or equipment. Theextraction is carried out by bringing the dimethyl ether into intimatecontact with the foodstuff and separating the dimethyl ether extractantsolution containing the extracted fat and/ or water from the insolubleresidue. The dimethyl ether is in liquid form as it is brought intocontact with the foodstuff, remains in the liquid form throughout theprocess, and is separated in the liquid form. Following separation, anyresidual dimethyl ether traces in the foodstuff readily evaporate atordinary pressures and temperatures, although elevated temperatures orvacuums are not precluded.

It is desirable to have the foodstuff in some comminute form prior tothe dimethyl ether extraction in order to ensure proper contacting ofthe fat and/or water to be extracted. For this purpose the foodstuff maybe ground as, for example, by putting meat through a grinder. In likemanner vegetables may be ground or they may be shredded in order topreserve desirable texture. In some cases foodstuffs may be cut intothin slices or small cubes or other shapes of appropriate dimensionssufficient to give effective extraction. The comminuting may be carriedout in the presence of dimethyl ether and the two operationsaccomplished at'one time.

The comminuted foodstuffs are subjected to the extraction by contactingwith the dimethyl ether, as already mentioned. The extraction may beeffected by mixing the foodstuff and the dimethyl ether together.Shaking or stirring of the mixture is usually desirable to improve theefficiency of the extractive operation. Although the solvent extractionis conveniently carried out on a batch basis, it is also possible toemploy a continuous process.

For example, the foodstuffs and the dimethyl ether may be fed into acontacting zone and the dimethyl ether extractant solution and theextracted foodstuff continuously withdrawin in separate streams.Countercurrent extraction processes in which the foodstuff and thedimethyl ether are circulated in the contact zone in counter'flow to oneanother may be used.

After the foodstuff and the dimethyl ether have been contactedsufficiently to provide the desired extraction, the extractant solutionand the foodstuff are separated by conveniental procedures. In aparticular method the foodstuff and the dimethyl ether mixture isallowed to separate by gravity and the dimethyl ether extractantsolution is withdrawn in liquid form. Other means of separation such asdecanting, centrifugation and filtering may also be used provided thatthe dimethyl ether extractant solution is maintained in liquid form. Thedimethyl ether extractant solution is easily separable, usually bydistillation. The dimethyl ether is readily recoverable for recycling tothe porcess or other use. The steps of extraction and separation may berepeated as often as necessary to obtain a residue having'the desiredfat and water concentration. Usually a number of stages of from 1 to 50and higher is satisfactory for a batch process.

Although the extraction method of the present invention has severaladvantages in that no complicated heating and pressuring procedures arerequired, it is necessary that the dimethyl ether be in substantiallyliquid form in order to provide proper contact with the fat and/ orwater to be extracted from the foodstulf. Since most of the fat andwater would be left in the residue if the dimethyl ether is withdrawn byevaporation, it is necessary that the dimethyl ether extractant solutionbe separated in liquid form. Suitable temperatures and pressures arereadily maintainable to keep the dimethylether in substantially liquidform.

The extraction of foodstuffs by contacting with dimethyl ether inaccordance with the method of this invention is carried out usuallywithout heating. Desirably the process permits the use of moderate andlower temperatures which do not adversely affect the flavor and textureof the foodstuff. In the preferred embodiment of the process the solventextraction is carried out at tempeatures below about 30 C. Although thepressures employed during the process may vary, it is preferred thatthey be suflicient to maintain the dimethyl ether in substantiallyliquid form. Autogeneous pressures are generally sufiicient for thispurpose.

Examples of foodstuffs which are effectively treated in accordance withthe method of this invention include meat of all kinds, fish, poultry,eggs, milk solids, cheese, vegetables such as beans, rice, nuts andpotatoes, any of which may be either cooked or uncooked.

Following the defatting and dehydrating of the foodstuif by the methodof the invention, some further processing may be desired. For example,the extracted foodstuff may be heated or irradiated as desired todeactivate enzymatic materials which can catalyze further change in theextracted foodstuff. Also other materials may be added to the extractedfoodstuff such as food colors and antioxidants. As an illustration,small amounts (about 0.01%) of the FDA-approved commercial antioxidantbutylated hydroxytoluene, known as BHT, may be employed to preventundesirable oxidizing deterioration.

The following examples are further illustrative of the improved methodof concurrently defatting and dehydrating foodstuffs of natural originin accordance with this invention, as well as the foodstufis derivedtherefrom. Unless otherwise specified, the proportions in theillustrative examples are on a weight basis.

EXAMPLE l-One step extraction A Fischer-Porter bottle having a volume of300 ml. was charged with 70 grams of ground beef. The bottle was thenconnected to a valve assembly, and 135 grams of dimethyl ether wasadded. The valve was closed, and the bottle was shaken at 48 cycles/min.for minutes. At the end of this time, the liquid phase was separatedfrom the solid meat phase by filtration and removed. The dimethyl etherextract was analyzed and found to contain 7.9 grams of water and 2.8grams of fat. The meat used for this experiment contained 6.5 grams offat and 45.9 grams of water. Therefore a single extraction using about a2:1 weight ratio of etherzmeat removed 44% of the fat and 17% of thewater.

EXAMPLE 2-Six step extraction Using the apparatus and procedure ofExample 1, 100 parts of ground beef was extracted with six separate butapproximately equal portions of dimethyl ether totaling 1285 parts. Allether extracts were combined and analyzed for 53.3 parts of water andfor 27.3 parts of fat.

The extracted meat was placed in a funnel through which was passed astream of nitrogen for V2 hour to remove the last traces of dimethylether. The insoluble residue resulting from this treatment weighed 19.4parts. It was analyzed for water and for fat by methods 23.003,

23.005, and 22.033 appearing in the Official Methods of Analysis. of theAssociation of official Agricultural Chemists, 10th. ed. published in1965. This analysis showed 0.3 part of fat and 1.9 parts of moistureremaining. The original meat contained 27.6 parts of fat and 55.2 partsof water. Therefore, a six stage extraction removed 99% of the fat and97% of the water.

EXAMPLE 3-Extraction with isopropyl alcohol A portion of ground beeffrom the same source as in Example 2, 100 parts, was extracted with sixseparate but approximately equal portions of isopropyl alcohol totaling1346 parts of water and 15.4 parts of fat. Thus, under conditionscomparable with those of Example 2, an isopropyl alcohol extractionremoved only 56% of the fat and 99+% of the water.

The insoluble extracted meat residue required drying in a vacuum oven at40 C. under 200 mm. of pressure for 36-48 hours for the removal of alltraces of isopropyl alcohol.

This example illustrates that although isopropyl alcohol is an excellentdehydrating solvent it is very much inferior to dimethyl ether indefatting. Furthermore, the example shows that long term heating undervacuum is necessary to completely remove the isopropyl alcohol solvent.By contrast, a period of only /2 hour at ambient temperature andpressure is satisfactory for the removal of dimethyl ether.

EXAMPLE 4-Two solvent extraction Using the apparatus and procedure ofExample 1, 70'

grams of ground beef was extracted with three approximately equalportions of isopropyl alcohol totaling 465 grams. The three extractswere combined and analyzed for 38.4 grams of water and 1.14 grams offat. Then the meat was extracted with three approximately equal portionsof dimethyl ether totaling 451 grams. These three extracts contained12.1 grams of water and 2.9 grams of fat. The total water removed was50.5 grams and the total fat removed was 4.05 grams.

The insoluble residue was dried and analyzed as in Example 2. Thisresidue weighed 15.4 grams and contained 0.76 gram of water and 0.14gram of fat. Thus, the extraction, first by isopropyl alcohol and thenby dimethyl ether, removed 99% of the moisture and 97% of the fat.

EXAMPLE 5Extraction with diethyl ether Ground beef was analyzed andfound to contain 68.5% water and 8.8% fat. This meat, 70 grams, wasextracted by the method of Example 2 using six separate butapproximately equal portions of diethyl ether totaling 900 grams. Theether extracts were combined and found to contain 11.5 grams of waterand 4.8 grams of fat. Thus, a six-stage extraction procedure utilizingdiethyl ether as the solvent removed only 24% of the water and 77% offat. Under the same conditions, dimethyl ether typically simultaneouslyremoves over of both the fat and water from treated foodstuffs.

The insoluble residue required drying for 1% hours at 40 C. in order toremove all traces of the ethyl ether solvent.

EXAMPLES 6 THROUGH 8-Extractions of other foodstuffs The followingexamples were carried out using the apparatus, procedure and analyticalmethods of Examp e 2.

Insoluble Percent Protelnaceous material Dimethyl residue, extractedExample her, H2O, number Type Grams grams percent Water Fat 6 Groundchicken breast..- 107.2 1,060 22.3 91 91 7..- on filet 63.1 1,036 23.096 96 8 Fresh egg, whole 57. 9 835 16. 7 98 98 EXAM-F LE9-Reconstitution of extracted foodstufl? TABLE II The product of Example2, 15 grams, was mixed with standard Pseudoabout 59 grams of water andformed into a patty. This p e C i m monas Methox ethaneco t ttime t60 tpatty was fried with peanut 011 sutficrent to prevent 15 i j nums mac 8whi 1 1 111 wh e 12i: m 1i: sticking in a skillet. The cooked productcompared to Untreated 1 100,000 1 230, freeze dried cooked hamburger wasmore edible and had 1 3,200 233 more desirable taste as determined by apanel of four 1% g2 38 persons. 100 Neg. 10 EXAMPLE IO-Storage stabilityNeg. 10

A sample of meat residue prepared as in Example 2 was stored in ascrew-capped jar at ambient temperature for 3 months. At the end of thistime, a total bacterial count analysis showed that the stored materialcontained less than 100 bacteria per gram and no mold at all.Ordinarily, edible fresh ground beef has a bacteria count of about 10per gram. Thus, this example demonstrates that the present processeffectively removes fat and water from a foodstuff and eliminatesbacteria and mold. The complete absence of bacteria and mold after 3months storage shows that the food residue has a substantial shelf-life.The product can, therefore, be easily transported from the producer tothe consumer without spoilage and at minimum cost.

The following examples further illustrate the sterilization withmethoxymethane in accordance with the present invention. Unlessotherwise indicated, percentages are on a weight basis.

EXAMPLE 11Sterilization of milk A number of experiments were carried outto evaluate methoxymethane as a sterilizing agent for milk and tocompare the results of this method of sterilization with thermalsterilization. In each experiment fresh, raw milk was placed in alaboratory pressure bottle. Methoxymethane was then added as a vaporfrom a pressure cylinder until the pressure in the laboratory bottlereached the desired test pressure. After addition of the methoxymethanethe bottle was sealed and shaken for the desired test time in a variablespeed laboratory shaker. The pressure was then released and themeth'oxymethane removed by venting. For comparative purposes a sample ofthe same milk was heat sterilized in a sealed laboratory pressure bottleby heating for minutes at 240-259 F in a laboratory pressure autoclave.

Bacteria counts were run on the milk, both before and after treatment,according to Standard Methods for the Examination of Dairy Products,12th ed., American Public Health Association, Inc.

Typical results are given in the following table:

Effect of methoxymethane contact time was determined by treating rawmilk with methoxymethane at 60 p.s.i.g. for different time periods usingthe laboratory procedure outlined above.

TABLE III Standard plate count,

cells/ml.

Pseudo- Coliform monas count cells/ml.

Untreated milk Immediately after methoxyrnethane treatment After oneweek at 70 F. =l=5 F.-... After two weeks at 70 F. =i=5 1!... After fourweeks at 70 F. i5 F.

The test results in the above examples show that the methoxymethane iseffective in controlling bacteria in milk. Although conditions of timeand temperature of contact and concentration are variable depending onthe particular microorganism, it may be seen that a substantialreduction in bacteria is obtained with contact times as short as 5minutes and pressures of as little as about 30 p.s.i.g.

Other experiments were carried out to demonstrate the effect ofconcentration of methoxymethane in the sterilization of milk. A mixtureof Lactobacillus bulgaricus (a yoghourt organism), Streptococcuscremoris (cottage cheese organism), and Escherichia coli (member of thehuman intestinal flora) in nonfat milk were sterilized at 23 C. Theexposure time was one hour at pressures of 15, 30 and 58 p.s.i. Therewas additional time during charging and venting of 0.3 hour at 15p.s.i., 0.7 hour at 30 p.s.i., and 1 hour at 59 p.s.i. Viable countswere performed on selective media that could distinguish amongsurvivors. Typical results are given in the following table.

Viable 15 p.s.i. 30 p.s.i.

58 p.s.i.

The above test results show that at about 15 p.s.i. partial pressure,'which is equivalent to about 6% methoxymethbut at a partial pressure of30 p.s.i., equivalent to about 12% in water, two of the threemicroorganisms were killed. At 58 p.s.i.,equivalent to about 24% byweight methoxymethane in water, all three of the microorganisms testedwere killed.

ane in water, the particular organisms were not killed,

EXAMPLE l2Sterilization of grape juice Fresh grapes purchased at a localgrocery store were crushed in a laboratory grinder. To make sure yeastswere present, the mixture was then inoculated with a small amount ofpurchased wine yeast culture. A sample of the whole crushed productincluding juice, pulp, seeds, and skins was placed in a laboratorypressure bottle; and methoxymethane was added as a gas from a pressurecylinder until the pressure in the laboratory bottle reached 60 p.s.i.g.The bottle was then sealed and shaken for one hour in a variable speedlaboratory shaker. The pressure was then released and the methoxymethaneremoved by venting.

Examination of the crushed grapes for yeasts and molds followingresults:

EMMPLE 13Sterilization of fermenting wine A sample of fermenting whitewine obtained from a local California winery was placed in a laboratorypressure bottle. Methoxymethane gas was added from a pressure cylinderuntil the pressure in the bottle reached 62 p.s.i.g. The bottle was thenshaken for one hour under pressure in a variable speed laboratoryshaker. At the end of this time, the pressure was released and themethoxymethane vented from the bottle.

Samples of the original wine and the methoxymethanetreatedwine were thenplated out on grape nutrient agar and incubated at 70 F. After 24 hoursthere was growth from the original, untreated sample; and the yeastflora was reported as viable. Centrifuged sediment from the originalsample was examined microscopically, and the cells observed appeared tobe normal.

After 144 hours there was no growth from the methoxymethane-treatedsample. Centrifuged sediment from the treated sample was also examinedmicroscopically. The yeast cells observed appeared to have a granulatedprotoplasm, and there was no evidence of budding.

EXAMPLE l4-Sterilization of meat In a laboratory bottle 100 parts ofground beef was extracted and sterilized by contacting with six separatebut approximately equal portions of liquid methoxymethane, totaling1,285 parts. In the extraction and sterilization the bottle is added.The valve is closed and the bottle shaken at 48 cycles per minute forminutes. The liquid phase is separated from the solid meat phase byfiltration and removed.

The extracted and sterilized meat was placed in a funnel through whichwas passed a stream of nitrogen for one-half hour to remove the lasttraces of methoxymethane. The insoluble residue resulting from thistreatment weighed 19.4 parts.

A sample of the meat residue obtained above was stored in a screw-cappedjar at ambient temperature for three months. At the end of this time atotal bacterial count analysis showed that the stored material containedless than 100 bacteria per gram and no mold at all. Ordinarily ediblefresh ground beef has a bacteria count of about 10 per gram. Thus thisexample demonstrates that the present process elfectively eliminatesbacteria and mold from meat and effectively preserves the food as shownby the complete absence of bacteria and mold after three months storage.

10 Table VI further illustrates sterilization experiments by giving theresults of bacteriological inspection of a number of solid food productskept in closed containers at room temperature after sterilization withmethoxymethane using the procedure outlined in Example 14.

Additional experiments were also carreed out to demonstrate themethoxymethane sterilization method of the invention employing thissterilizing agent in the gaseous state.

EXAMPLE 15Sterilization of glass objects Two silicon rubber rings, 2 cm.in diameter, were mounted on one side of a standard glass microscopeslide. The slide was then glued to a polyurethane-rubber spongesaturated with water. This combination was heat sterilized, after whichone drop of a Straphylococcus aureus culture having 88x10 cells/ml. wasplaced within each ring. The inoculated slide mounted on the moistsponge was then placed in a sterile Fischer-Porter bottle to which therewas attached a gas inlet device. The bottle was charged to 60 p.s.i.g.with methoxymethane and held for two hours at ambient temperature. Atthe end of this time, the bottle was vented. A bacteria count of theslide showed complete sterilization. No germs were found by a testcapable of detecting as few as 10 cells/ml.

A comparison slide treated in the same way as described above, exceptthat it was not exposed to methoxymethane, tested for 69 10 and x10cells/ml. at the end of the experiment.

EXAMPLE l6Sterilization of gauze The procedure of Example 11 wasfollowed, except that an unmedicated gauze Band-Aid was pinned to theurethane-rubber sponge. At the end of the test period, the Band-Aidexposed to methoxymethane was sterile (less than 10 cells/ml.); whereasthe comparison gauze had a Staphylococcus aureus count of 114x10 cells/ml.

The results in the above experiments show that methoxymethane iselfective in the gaseous state since complete or substantially completesterilization is obtained, as it was in the previously mentionedexperiments demonstrating the elfectiveness of methoxymethane in liquidstate, either as pure methoxymethane or as aqueous solutions ofmethoxymethane. It was noted that in both EX- ample 15 and Example 16the systems had an appreciable moisture content in the form of watervapor as evidenced by some condensation on the inside walls of theFischer- Porter bottle.

While the character of this invention has been described in detail withnumerous examples, this has been done by way of illustration only andwithout limitation of the invention. It will be apparent to thoseskilled in the art that modifications and variations of the illustrativeexamples may be made in the practice of the invention within the scopeof the following claims.

What is claimed is:

1. A method for simultaneously defatting, dehydrating, and eliminatingbacteria from solid and liquid foodstuffs containing fat and/ or waterand bacteria which comprises intimately contacting the foodstuffs withliquid dimethyl ether in an extraction zone under a pressure suflicientto maintain the dimethyl ether in liquid phase and withdrawing liquiddimethyl ether containing any extracted water OTHER REFERENCES and fatfrom the extractlor} zone; Rose et al., The Condensed ChemicalDictionary, 5th

The method of clam 1 19 Much the foodstufi 18 ed, 1956, p. 391, articleentitled Dimethyl Ether. Copy in group 172, US. Pat. Off.

References Cited 5 HYMAN LORD P E UNITED STATES PATENTS xammer 2,539,5441/1951 Levin et a1. 99208 3,520,868 7/1970 Henderson et a1. 99208 X426--442, 429

. UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,795 ,750 Dat d March 5; 1974 Inventor(s) Irving E. Levine It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

a Column 8, line 55, "59 p.s.i-." should read 58 p.s.i.-

Column 9, linelS, after "molds" add --'-before and 1 and aftermethoxymethane treatment gave the-- a line 56, after "is", firstOccurrence 7 add -connected to a valve assembly through which .themethoxymethane isl Signed and sealed this 17th day of September 1974.

(SEAL) Attest:

MCCOY M. GIBSON 'JR. 0. Attesting Officer MARSHALL DANN Commissioner. ofPatents

